1. Technical Field
This application relates to computer storage devices, and more particularly to the field of transferring data between storage devices.
2. Description of Related Art
Host processor systems may store and retrieve data using a storage device containing a plurality of host interface units (host adapters), disk drives, and disk interface units (disk adapters). Such storage devices are provided, for example, by EMC Corporation of Hopkinton, Mass. and disclosed in U.S. Pat. No. 5,206,939 to Yanai et al., U.S. Pat. No. 5,778,394 to Galtzur et al., U.S. Pat. No. 5,845,147 to Vishlitzky et al., and U.S. Pat. No. 5,857,208 to Ofek. The host systems access the storage device through a plurality of channels provided therewith. Host systems provide data and access control information through the channels to the storage device and the storage device provides data to the host systems also through the channels. The host systems do not address the disk drives of the storage device directly, but rather, access what appears to the host systems as a plurality of logical disk units. The logical disk units may or may not correspond to the actual disk drives. Allowing multiple host systems to access the single storage device unit allows the host systems to share data stored therein.
In some instances, data from a local storage device is replicated to a remote storage device via one or more replication links connecting the storage devices. In some cases, multiple processes at the local storage device may independently provide remote replication and thus may be sharing the one or more of the replication links. The processes may have different replication modes (e.g., synchronous, asynchronous, data mobility, etc.), with different quality of service requirements. However, it may be difficult to determine appropriate resource allocation between the different processes when the service requirements are not directly comparable (e.g., a specified lag time for a process that uses asynchronous replication vs. a specified response time for a process that uses synchronous replication). In addition, it may be difficult to estimate an effect on replication link capacity of each of the processes so that it is difficult to determine an appropriate amount of link capacity resources to allocate to each of the processes.
Accordingly, it is desirable to provide a mechanism that facilitates sharing a link among a plurality of processes that transmit data to a remote storage device where the link resources used by each of the processes may be determined irrespective of the mode used for replication.